I’m going to a concert here in April and if the Gates/ Doors open at 6:30 and I want to be as far up in the line as possible what time should I get there?

The more popular the band the earlier you should get there. But a hour or 2 should be good

For most bands an hour early is fine. Check for tickets a few days before the show. If it's almost sold out, maybe a little earlier.

5:30 if it's a popular band

Depends on the group